Catalytic dehydrogenation of alcohols



Patented June 7, 1949 CATALYTIC DEHYDROGENATION OF ALCOHOLS Helmuth G.Schneider, Westfleld, and Vincent F.

Mistretta, Fanwood, N. J assignors to Standard Oil Development Company,a corporation I v of Delaware No Drawing. Original application December28, 1944, Serial No. 570,210, now Patent No. 2,436,733, dated February24, 1948. Divided and this application September 29, 1945, Serial No. a

8 Claims. ((31. 260-596) 1 This application is a divisional applicationof Serial No. 570,210, filed December 28, 1944, which issued as PatentNo. 2,436,733.

The present invention relates to improved catalysts and moreparticularly to improved catalysts useful for instance in the conversionof secondary alcohols to ketones.

It is well known that the dehydrogenation of secondary alcohols to thecorresponding ketones may be achieved by passing the alcohols atelevated temperatures over substances acting as dehydrogenationcatalysts. In the early stages of development in this field, metals suchas copper, brass, etc. were employed in this type of reaction. Thesecatalysts possess the disadvantages of high operating temperatures andshort life. Somewhat later, difilcultly reducible oxides such as zincoxide, cerium oxide, magnesium oxide, etc., attained considerableprominence as dehydrogenation catalysts. Various combinations ofcatalytic metals and difficultly reducible oxides have also beenemployed from time to time. It was found that difficultly reducibleoxides have a dehydrating as well as a dehydrogenating eiiect and thatdue to the dehydrating effect, considerable olefin was regenerated fromthe alcohol which reduced the overall-yield of ketone. In an attempt tominimize these side reactions, additives such as the alkali or alkalineearth metal carbonates or hydroxides have been employed in conjunctionwith the diiiicultly reducible oxide catalysts. In instances where theseadditives have been used it has been noted that they make the catalystthermally less stable, thus reducing its life and increase. thesusceptibility of the catalyst to catalyst poisons. v

The object of the present invention is to increase the activity ofdifiicultly reducible oxide catalysts as dehydrogenation catalysts,particularly for the dehydrogenation of compounds containing the organicgrouping R-CHOH-R1.

Another object is to improve the stability of dehydrogenation catalystsat high temperatures. Still another object is to make diflicultlyreducible oxide catalysts more resistant to catalyst poisons thuslengthening the active life of the catalysts. These and other objectswill be apparent to those skilled inthe art upon reading the followingdescription.

These objects are accomplished by the following invention, which in itsgeneral aspect, com-' prises the employment of bismuth oxide inconjunction with diflicultly reducible oxide dehy drogenation catalystsof which zinc oxide, cerium oxide and magnesium oxide are examples; Ithas .2 now been found' that from 1% to 6% of bismuth oxide, B1203, basedupon the weight of dimcultly reducible oxide used, preferably about.6%,greatly improves the action of the difficultly reducible oxide as adehydrogenation catalyst in reactions involving compounds having theformula methyl, phenyl or cyclohexyl. The improvement obtained by usingless than 1% of bismuth oxide is perceptible, but not suflicient to beof any material consequence, while the improvement engendered by the useof more than 6% of bismuth oxide is not suflicient over that obtainedwhen using about 6% to warrant the additional expenditure.

Taking the preparation of ZnO--Bi20s catalyst as typical of thecomposition of this invention, it is preferred practice to mix the twooxides in the proper proportions in powdered form, then work in enoughwater to make a heavy slurry of the oxides, the slurry to be about theconsistency of heavy cream. This will ordinarily require a volume ofwater approximately equivalent to the volume of powder used. Thecatalyst slurry is then coated on a carrier. This is convenientlyaccomplished by putting the catalyst support or carrier in a tumblingmechanism, pouring the catalyst slurry over the carrier and thentumbling until a uniform mix is secured. The mix is then placed in anoven at 80 C. and dried.

The drying step generally requires from 24 to 48 The conversion ofsecondary alcohols to ketones is accomplished by passing the alcohol invapor form through a catalyst packed tube heated to the temperature from350 to 500 C. ,at a pressure of from about 10-40 pounds per square inchand a feed or feed rate of from 0.5 to 10 volumes of liquid alcohol pervolume of catalyst per hour.

The vapors are then passed to a condenser where the ketone and unreactedalcohol are condensed from the less readily condensible gases consistingpredominantly of hydrogen and a small amount Tarium. Brimrur! Example 4The ZnO-BizO: catalyst can withstand exof, rdinarll n m r 1 re eneratedOlen; y o e than g treme variations in temperature without appreg ree ofentertainers"; ears"; start:- ven on, e o ng exampes w c are neludedmerely for purposes of illustration and lated to catalyst life and isimportant from a not as a limitation, of the conversion of sec-l0commercla Point of View in that temperature ondary t l l h l t methylethyl ketone fluctuations and shutdowns will not be of serious under theconditions indicated in each example, consequence when'a filo-B1203catalyst 15 graphically demonstrate the superiority of the Pyed- 7present catalyst with respect to activity at high In order to test thethermal stability of the throughput, optimum temperature of reaction,catalysts 3 were f 3 Period of 5 thermal stability, longer life andresistance to 238 gig i-r /s-/ f g zg f i t g i on o o O a Sqp0 in.gauge.

- CATALYTIC ACTIVITY The increased activity of ZnO catalyst fortified yz o z O with 31:03 is clearly demonstrated in Example 1 Catalyst(011M855) h2g8? 152 below, which shows that ZnO-BiaOs at high feed ratesmaintains a conversion at a 90% level p t o i t k mnestwhereas ZnO aloneand ZnO-i-NazCO: catalysts 8: 35-8 2% g gdrop to 70%. Example 2 Simflf115/ shows the 400c1IIIIIIIIIIIIIIIIIIIIII 78:0 csfo solo improvedcatalytic activity of ZnO-BlzOs cata- 1 st with radual increased feedrates.

y g Catalyst (on pumico)..... ZnO gg'g? M13319? Example 1iTempAoooorzflsq-migauge'l PEI'EIgEEOllI-VQISIOHtOkGtOXlGBP- 406%-: .1c410 1210 in) Catalyst (on pumice) ZnO g g? 5%;

CATALYST LIFE Percent mnv ersiontoketone att338i:2i&llff:::::::: 53:335:8 $13 The ZHO-B1ZOI catalyst possesses a 10118 active life than otherconventional catalysts. Example 2 This is shown by an accelerated lifetest, run simultaneously in the same heating bath with [Temp.400C.-2#/sq. in. gauge] the same alcohol feed. This accelerated test wasperformed to demonstrate, under adverse e Z 0+6 2 0 6% conditions forthe ZnO-BizOa, that a longer accamysmn 13sec? 111:6; tive life ischaracteristic of the B1203 fortified catalyst. The ZnO-NazCOa catalystat in- Poriicgtoi mvelsionwkemfl at- 40 creased feed rate converts only70% of the al- $173155: 3;;3 32 3 cohol charged to ketone whereasZIlO-Bi20: -g f ig gg-g 33-8 catalyst maintains a 90% conversion. Anydecrease in activity, therefore, would be much more noticeable with theZnO-BizOa catalyst. The increased activity of ZnO-BlzOa is further Theresults are illustrated in Example 5 below. revealed 1n Example 3 belowwhich shows that which clearly shows the longevity of the for a givenconversion of alcohol to ketone the ZnO Bi2O3 catalyst B1203 fortifiedcatalyst permits a. lower operating temperature. This holds true atnormal and Example 5 higher than normal feed rates. [Temp 400 C 2sq mgaugHv/v/hr Md mm] Exam le 3 p Zn0+6% Zn0+6% [Feed rate 1.5v./v./hr.-2#lsq. in. gauge.] Days on Stream gg gg P316081! 0 .E. .E.Catalyst n br ss) @333? figa 0 92 o as its "ttt fil?f fiiiiiiffffi gg g353 e 9210 51% I [Feed Rate 6.0 v./v./Hr.2#lsq. in. 81:11:91 Y 5% Egg,no sale Catalyst (on brass) fig''g? ig gr Rasrsranca r0 men-anus m FunBrocx Percent cmversion to ketone at 99 31 33%03:33::::::::::::::::::::::?::::: 43:3 e33 r a given lcoh qu ity a dimultly r ble oxide dehydrogenation catalyst containing 76 B110: exhibitsa marked resistance to poisons.

5. The secondary butyl alcohol used for illustrative purposes had thefollowing compositions.

1. The method of producing ketones which comprises passing a secondaryaliphatic alcohol over a catalyst composed of zinc oxide and 16% byweight 3120s under conversion conditions of temperature and pressure.

I 2. The method or producing ketones which comprises passing a secondaryaliphatic alcohol over a catalyst composed of zinc oxide and 6% byweight B1203 under conversion conditions of temperature and pressure.

3. The method of producing methyl ethyl ketone which comprises passingsecondary butyl alcohol over a catalyst composed of zinc oxide and 1-6%by weight B1203 under conversion conditions of temperature and pressure.

4. The method of producing methyl ethyl ketone which comprises passingsecondary butyl alcohol over a catalyst composed of zinc oxidev and 6%by weight B1203 under conversion conditions of temperature and pressure.

5, The method of producing methyl ethyl ketone which comprises passingsecondary butyl alcohol at about 15 pounds per square inch pressureabsolute and at a feed rate of about 4-6 v./v./hour over a catalystcomposed of a mixture of zinc oxide and 6% by weight B1203 on a catalystcarrier heated to a temperature of 350- 500C.

6. The method of producing methyl ethyl I ketone which comprises passingsecondary butyl alcohol at about 15 pounds per square inch pressureabsolute and at a feed rate of about 4-6 v./v./hour overa catalystcomposed of amixture of zinc oxide and 6% by weight BizOs on a catalystcarrier heated to a temperature of 400 C.

7. The method of producing ketones which comprises passing a secondaryaliphatic alcohol over a metal oxide dehydrogenation catalyst selectedfrom the group consisting of zinc oxide, cerium oxide and magnesiumoxide and 1 to about 6% by weight of bismuth oxideunder conversionconditions of temperature and pressure.

8. The method according to claim '7 in which methyl ethyl ketone isprepared from secondary butyl alcohol.

HELMUTH G. SCHNEIDER. VINCENT F. MISTREIIA.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

